Giant piezoelectricity and ferroelectricity in two-dimensional ThOTe monolayers

Abstract

Two-dimensional flexible materials with both piezoelectric and ferroelectric properties are regarded as the holy grail for realizing ultrathin functional electronic devices, which can be used in electronic flexible skin, high-performance storage, and medical diagnostic devices. However, the piezoelectric coefficients found in current two-dimensional (2D) piezoelectric-ferroelectric materials are comparatively limited in magnitude. Based on first-principles calculations, we demonstrate that 2D ThOTe monolayers exhibit not only remarkable flexibility in their mechanical properties (K/G > 1.75), but also exceptional piezoelectric and ferroelectric characteristics when subjected to strain engineering. Especially, they display an extraordinarily large piezoelectric constant, e₁₁ = 13 181.19 pC m⁻¹, and an impressively high piezoelectric coefficient of d₁₁ = 354.95 pm V⁻¹ at a tensile strain of 14%. Simultaneously, we discovered that the ThOTe monolayer possesses ferroelectric properties with an intrinsic electrode polarization, primarily aligned along the x-axis. The results introduce an innovative approach to explore ferroelectric materials within giant piezoelectric substances and provide valuable insights and references for the development of high-performance giant piezoelectric sensors, electronic devices and memories.